The relationship between the development of vision and the development of eye movements is a reciprocal one: each affects the other. Oculomotor disorders (e.g., strabismus and nystagmus) can have marked, deleterious effects on the development of vision. Although there is a body of literature concerning the development of vision, very few quantitative data are available about the development of eye movements. Our overall objective is to carry out a quantitative analysis of the developmental roles of vestibular, smooth pursuit and optokinetic eye movement systems in maintaining a stable image on the retina for visual processing during head movements in infants and young children. The data should provide clinicians a better understanding of how oculomotor disorders influence the development of vision in young infants. Specific Aims: 1. To quantify the developmental progression of smooth pursuit and optokinetic eye movements at selected intervals from early infancy to adulthood. 2. To study quantitatively the potential interaction of smooth pursuit and optokinetic eye movements with the vestibulo-ocular reflex in conditions similar to those used to study the development of the vestibulo-ocular reflex and visual-vestibular interactions in our current experiments. 3. To quantify the development of optokinetic after-nystagmus and the velocity storage integrator, using Cohen's analytical procedures. 4. To measure each eye independently in tests of both smooth pursuit and optokinetic eye movements and to ascertain the effects of conjugacy on the initiation of the eye movements and on the gain of the system.